The present invention relates to improvements in an electrical discharge machine for forming a small hole in a workpiece by electric discharge energy when electric power for machining is supplied to between the electrode for forming a small hole and the workpiece so as to form a small hole in the workpiece by the electric discharge energy.
An electrical discharge machine for forming a small hole is used for the purpose of forming a hole with high accuracy because roundness and uniformity of a hole formed by the electrical discharge machine are higher than those of a small hole formed by laser beam machining. In the case of forming a large number of small holes (for example, about 10,000 small holes, the diameter of which is 0.1 mm) in a workpiece, a highly reliable automatization is required.
Concerning the electrode for forming a small hole used for an electrical discharge machine, a thin wire made of copper or tungsten is used. Since the electrode for forming a small hole is intensely consumed in the process of electrical discharge machining, in order to prevent the productivity from deterioration, it is necessary to use a long electrode for forming a small hole (for example, the diameter of which is approximately 0.1 mm and the length of which is approximately 200 mm). Since the electrode for forming a small hole is very thin and long as described above, deflection tends to occur and it is difficult to handle the electrode. Therefore, when a small hole is formed with this electrode, problems occur in which the machining accuracy and reliability are deteriorated.
In order to stabilize the operation of machining by discharging sludge and also in order to enhance the roundness, for example, the electrode for forming a small hole is used while it is being rotated at a rotational speed of about 1,000 rpm. Therefore, deflection of the electrode for forming a small hole tends occur in the process of electrical discharge machining. When electric discharge machining is conducted under the condition that deflection is caused in the electrode for forming a small hole, there is a problem that a predetermined machining accuracy can not be obtained because it is impossible to appropriately conduct the feed of an electrode that is necessary in accordance with the detritions of the electrode.
FIG. 6 is a schematic illustration showing the constitution of a conventional electrical discharge machine for forming a small hole, which is disclosed in Japanese Unexamined Patent Publication No. 60-108234 aimed to solve the above problems. In the drawing, reference numeral 1 is an electrode for forming a small hole, reference numeral 2 is a workpiece, reference numeral 3 is a table, reference numeral 4 is a main shaft, reference numeral 5 is a chuck, reference numeral 6 is a an electrode holder for holding the electrode 1 for forming a small hole, reference numeral 6a is a support arm, reference numeral 7 is a small hole guide having a small hole by which the electrode 1 for forming a small hole is guided, and reference numeral 8 is an intermediate guide. Between the electrode 1 for forming a small hole and the workpiece 2, there is provided a work liquid not shown in the drawing. Electric power for electrical discharge machining is supplied from an electric power source not shown to between the electrode 1 for forming a small hole and the workpiece 2. Thus, a small hole is formed in the workpiece 2 by the electric discharge energy.
An intermediate portion of the electrode 1 for forming a small hole is guided by the intermediate guide 8, and this intermediate guide 8 is driven by the support arm 6a, so that the intermediate guide 8 can be moved synchronously with the elevation of the main shaft 4 (as shown by arrow E in the drawing). In this way, deflection of the electrode 1 for forming a small hole caused in the process of electrical discharge machining can be suppressed. However, this constitution has such a problem that it is difficult to automatically replace the electrode 1 for forming a small hole because of the structure in which the intermediate guide 8 is driven by the support arm 6. Further, it is impossible for the above intermediate guide 8 to meet the recent demand of enhancing the accuracy.
FIG. 7 is a schematic illustration showing a constitution and operation of a conventional electrical discharge machine for forming a small hole disclosed in Japanese Unexamined Patent Publication No. 8-229747. In the drawing, reference numeral 1 is an electrode for forming a small hole, reference numeral 2 is a workpiece, reference numeral 3 is a table, reference numeral 4 is a main shaft, reference numeral 5 is a chuck, reference numeral 6 is a an electrode holder for holding the electrode 1 for forming a small hole, numeral 7 is a small hole guide, and reference numeral 9 is an introduction guide. There is provided a work liquid not shown between the electrode 1 for forming a small hole and the workpiece 2.
A primary object of this electrical discharge machine for forming a small hole is to automatically replace an electrode for forming a small hole. The summary of its operation will be described in the following items (1) to (4). (1) The main shaft 4 is raised, and the electrode 1 for forming a small hole is automatically replaced together with the electrode holder 6. After that, the induction guide 9 is raised to an upper portion of the electrode 1 for forming a small hole so as to loosely pinch the electrode 1 for forming a small hole as shown in FIG. 7(a); (2) While the electrode 1 for machining an small hole is being loosely pinched, the induction guide 9 is lowered to a lower portion of the electrode 1 for forming a small hole as shown in FIG. 7(b); (3) The main shaft 4 is lowered, and the electrode 1 for forming a small hole is inserted into a small hole of the small hole guide 7 as shown in FIG. 7(c); (4) The induction guide 9 is retracted outside the machining region of the workpiece 2 as shown in FIG. 7(d).
In the electrical discharge machine for forming a small hole having the above structure, it is possible to automatically replace the electrode for forming a small hole. However, it is impossible to suppress the occurrence of deflection of the electrode 1 for forming a small hole caused in the process of electrical discharge machining. Therefore, it is impossible to apply the electrical discharge machine for forming a small hole having the above structure to the use in which high accuracy is required.
In order to make rapid progress in science technology and strengthen industrial competitiveness in recent years, there is an increasing demand of enhancing the accuracy, productivity and reliability of an electrical discharge machine for forming a small hole. It is an object of the present invention to provide an electrical discharge machine for machining a highly accurate small hole, which is appropriate for automatization, by which the aforementioned problems are solved, being capable of enhancing accuracy, productivity and reliability.
An electrical discharge machine for forming a small hole of the present invention comprises: an electrode holder to hold an electrode for forming a small hole; a drive unit to drive the electrode holder and electrode for forming a small hole in the longitudinal direction; a small hole guide having a small hole to guide the electrode for forming a small hole, arranged close to a workpiece; and an electric power source used for electric discharge machining to supply electric power for electrical discharge machining between the electrode for forming a small hole and the workpiece, wherein a small hole is formed in the workpiece by electric discharge energy, and the electrical discharge machine for forming a small hole further comprises: an intermediate guide composed of at least two guides to hold the electrode for forming a small hole between the electrode holder and the small hole guide, each guide having a chuck capable of being opened and closed; a first drive unit to drive the intermediate guide in the longitudinal direction of the electrode for forming a small hole; a second drive unit to open and close the guide chucks of the intermediate guide; and a third drive unit to variably change a distance between the guides of the intermediate guide in the longitudinal direction of the electrode for forming a small hole.
An electrical discharge machine for forming a small hole of the present invention comprises: an electrode holder to hold an electrode for forming a small hole; a drive unit to drive the electrode holder and electrode for forming a small hole in the longitudinal direction; a small hole guide having a small hole to guide the electrode for forming a small hole, arranged close to a workpiece; and an electric power source used for electric discharge machining to supply electric power for electrical discharge machining between the electrode for forming a small hole and the workpiece, wherein a small hole is formed in the workpiece by electric discharge energy, and the electrical discharge machine for forming a small hole further comprises: an intermediate guide having a first guide to support the electrode for forming a small hole at a position close to the small hole guide and also having a second guide to support the electrode for forming a small hole at a position between the electrode holder and the small hole guide, the second guide having a chuck capable of being opened and closed; a first drive unit to drive the intermediate guide in the longitudinal direction of the electrode for forming a small hole; a second drive unit to open and close the chuck of the second guide of the intermediate guide; and a third drive unit to variably change a distance between the first and the second guide of the intermediate guide in the longitudinal direction of the electrode for forming a small hole.
An electrical discharge machine for forming a small hole of the present invention comprises: an electrode holder to hold an electrode for forming a small hole; a drive unit to drive the electrode holder and electrode for forming a small hole in the longitudinal direction; a small hole guide having a small hole to guide the electrode for forming a small hole, arranged close to a workpiece; and an electric power source used for electric discharge machining to supply electric power for machining between the electrode for forming a small hole and the workpiece, wherein a small hole is formed in the workpiece by electric discharge energy, and the electrical discharge machine for forming a small hole further comprises: an intermediate guide having a first guide to support the electrode for forming a small hole at a position close to the small hole guide and also having a plurality of guides except for the first guide to support the electrode for forming a small hole at positions between the electrode holder and the small hole guide, the plurality of guides except for the first guide having a chuck capable of being opened and closed; a first drive unit to drive the intermediate guide in the longitudinal direction of the electrode for forming a small hole; a second drive unit to open and close the chucks of the plurality of guides except for the first guide of the intermediate guide; and a third drive unit to variably change a distance between the first guide and each of the plurality of guides except for the first guide in the longitudinal direction of the electrode for forming a small hole.
An electrical discharge machine for forming a small hole of the present invention, further comprises a fourth drive unit to drive the small hole guide in the longitudinal direction of the electrode for forming a small hole.
An electrical discharge machine for forming a small hole of the present invention comprises a chuck capable of being opened and closed in the first guide of the intermediate guide.